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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2673) Investigate consistency of intra-row scans
Date Tue, 08 Jun 2010 03:04:11 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12876524#action_12876524
] 

Todd Lipcon commented on HBASE-2673:
------------------------------------

I thought about this a bit tonight. I think this is essentially impossible to implement unless
we do the following:
- Add logical timestamps to HFiles (a few bytes per KV if we use vints and relative to an
hfile-wide meta entry)
- Add to the scanner API so that each scan result object also returns the current logical
timestamp
- Add logical timestamps to HLog entries so that a server that replays the edits maintains
the same logical timestamps of each row.

I think these are all needed in order to maintain consistency in the face of failure or through
a flush operation.

Rather than do all of the above, I think we should simply document in Scanner.setBatch that
using intra-row scanning loses the consistency guarantee. Also we'll want to augment the acid
guarantees doc to state this.

> Investigate consistency of intra-row scans
> ------------------------------------------
>
>                 Key: HBASE-2673
>                 URL: https://issues.apache.org/jira/browse/HBASE-2673
>             Project: HBase
>          Issue Type: Task
>          Components: documentation, regionserver
>    Affects Versions: 0.21.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>
> I have an intuition that intra-row scanning probably does not provide a consistent view
of the row. We should investigate how true this is, and document what the interaction of the
feature is with the guarantee, etc.

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